diff --git a/patrole_tempest_plugin/tests/unit/test_rbac_policy_parser.py b/patrole_tempest_plugin/tests/unit/test_rbac_policy_parser.py
index e3a4429..95e6bff 100644
--- a/patrole_tempest_plugin/tests/unit/test_rbac_policy_parser.py
+++ b/patrole_tempest_plugin/tests/unit/test_rbac_policy_parser.py
@@ -40,8 +40,9 @@
 
     def setUp(self):
         super(RbacPolicyTest, self).setUp()
-        mock_admin_mgr = self.patchobject(rbac_policy_parser, 'credentials')
-        mock_admin_mgr.AdminManager().identity_services_v3_client.\
+        self.mock_admin_mgr = self.patchobject(
+            rbac_policy_parser, 'credentials')
+        self.mock_admin_mgr.AdminManager().identity_services_v3_client.\
             list_services.return_value = self.services
 
         current_directory = os.path.dirname(os.path.realpath(__file__))
@@ -57,14 +58,19 @@
         self.tenant_policy_file = os.path.join(current_directory,
                                                'resources',
                                                'tenant_rbac_policy.json')
+        self.conf_policy_path = os.path.join(
+            current_directory, 'resources', '%s.json')
 
         CONF.set_override(
-            'custom_policy_files',
-            [os.path.join(current_directory, 'resources', '%s.json')],
-            group='rbac')
+            'custom_policy_files', [self.conf_policy_path], group='rbac')
         self.addCleanup(CONF.clear_override, 'custom_policy_files',
                         group='rbac')
 
+        # Guarantee a blank slate for each test.
+        for attr in ('available_services', 'policy_files'):
+            if attr in dir(rbac_policy_parser.RbacPolicyParser):
+                delattr(rbac_policy_parser.RbacPolicyParser, attr)
+
     def _get_fake_policy_rule(self, name, rule):
         fake_rule = mock.Mock(check=rule)
         fake_rule.name = name
@@ -427,3 +433,60 @@
             .format('tenant_rbac_policy', [CONF.rbac.custom_policy_files[0]
                                            % 'tenant_rbac_policy']))
         self.assertIn(expected_error, str(e))
+
+    def test_discover_policy_files(self):
+        policy_parser = rbac_policy_parser.RbacPolicyParser(
+            None, None, 'tenant_rbac_policy')
+
+        # Ensure that "policy_files" is set at class and instance levels.
+        self.assertIn('policy_files',
+                      dir(rbac_policy_parser.RbacPolicyParser))
+        self.assertIn('policy_files', dir(policy_parser))
+        self.assertIn('tenant_rbac_policy', policy_parser.policy_files)
+        self.assertEqual(self.conf_policy_path % 'tenant_rbac_policy',
+                         policy_parser.policy_files['tenant_rbac_policy'])
+
+    @mock.patch.object(rbac_policy_parser, 'policy', autospec=True)
+    @mock.patch.object(rbac_policy_parser.RbacPolicyParser, '_get_policy_data',
+                       autospec=True)
+    @mock.patch.object(rbac_policy_parser, 'os', autospec=True)
+    def test_discover_policy_files_with_many_invalid_one_valid(self, m_os, *a):
+        # Only the 3rd path is valid.
+        m_os.path.isfile.side_effect = [False, False, True, False]
+
+        # Ensure the outer for loop runs only once in `discover_policy_files`.
+        self.mock_admin_mgr.AdminManager().identity_services_v3_client.\
+            list_services.return_value = {
+                'services': [{'name': 'test_service'}]}
+
+        # The expected policy will be 'baz/test_service'.
+        CONF.set_override(
+            'custom_policy_files', ['foo/%s', 'bar/%s', 'baz/%s'],
+            group='rbac')
+
+        policy_parser = rbac_policy_parser.RbacPolicyParser(
+            None, None, 'test_service')
+
+        # Ensure that "policy_files" is set at class and instance levels.
+        self.assertIn('policy_files',
+                      dir(rbac_policy_parser.RbacPolicyParser))
+        self.assertIn('policy_files', dir(policy_parser))
+        self.assertIn('test_service', policy_parser.policy_files)
+        self.assertEqual('baz/test_service',
+                         policy_parser.policy_files['test_service'])
+
+    def test_discover_policy_files_with_no_valid_files(self):
+        expected_error = ("Policy file for test_service service neither found "
+                          "in code nor at %s." %
+                          [self.conf_policy_path % 'test_service'])
+
+        e = self.assertRaises(rbac_exceptions.RbacParsingException,
+                              rbac_policy_parser.RbacPolicyParser,
+                              None, None, 'test_service')
+        self.assertIn(expected_error, str(e))
+
+        self.assertIn('policy_files',
+                      dir(rbac_policy_parser.RbacPolicyParser))
+        self.assertNotIn(
+            'test_service',
+            rbac_policy_parser.RbacPolicyParser.policy_files.keys())